Unfortunately I don't have M3. It'll need to fit quite well to look believable - it needs to pull tight around the neck and under the arm so it looks like it is taking the weight of the arm, and the tension creases need to be long and straight or they'll look fake. I think you'd have quite a job morphing it from one figure to another with the morph brush, probably easier to make it directly on your posed figure in wings or something.

Make the bit around the back of the neck, make the bit under the arm, bridge between them to make the front panel, copy the top of that to make the part against the chest, tweak a bit, done.